1. Field of the Invention
The present invention relates to the production of aluminum powder from scraps of aluminum and to multi-layer, porous materials produced therefrom for use in noise absorbing devices and filter elements for automobiles and air conditioners. More particularly, the present invention relates to a method in the preparation of multi-layer, porous materials comprising producing aluminum powder by a centrifugal atomization method from scrap aluminum and sintering the resulting aluminum powder with bonding materials.
2. Description of the Related Art
In accordance with industrial development, the demand for aluminum materials is increasing every year and the amount of scrap aluminum is also increasing. This not only contributes to public nuisances, but also many problems in terms of recycling. Currently existing methods of producing metal powder in large quantity use water atomization and gas atomization. Since materials like aluminum are easily oxidized and cannot be powdered by water atomization, aluminum powder is produced by gas atomization. The method of gas atomization, however, requires large facilities, which in turn require high maintenance costs. Therefore, the gas atomization method is not suitable for producing aluminum powder from scrap aluminum. Further, the use of noise absorbing materials that are now commercially produced can be largely classified into three categories, fiber shaped materials, sintered materials, and concrete materials. The sound absorbing material should have an efficient acoustic absorbing power, fire resistance, light weight, durability, hardness, and ductility. The fiber shaped sound absorbing materials like glass fibers, however, have the disadvantages of not only a poor forming capability due to weakness in hardness and durability of the materials, but also their sound absorbing effects are reduced when they are wet. The sintered sound absorbing materials, like ceramics, are heavy in weight and exhibit no ductility, and it is difficult to construct facilities/devices therefrom. Concrete sound absorbing materials have a poor efficiency in absorbing sound of high frequency. Sintered aluminum sound absorbing materials that have been recently developed are not only very expensive, but also very weak in absorbing sound in medium and low frequencies. In addition to the aforementioned inefficiencies, the sound absorbing materials of glass fiber and ceramics cannot be used for places of high vibration.